This invention relates to delay line correlators and more particularly to digital delay line correlators.
Delay line correlators known in the prior art including either analog delay lines or digital delay lines have been used to detect the pulse repetition interval (PRI) between the spaced pulses of a single sequence of time spaced pulses by means of a coincidence device (an AND gate) coupled to taps of the analog delay line or to flip flop stages of a digital delay line wherein the taps and flip flops are spaced along the delay line by the PRI intended to be detected.
Such delay line correlators find use in systems having a highly dense pulse environment such as encountered in navigation systems, such as TACAN, sonar systems, doppler radar systems, MTI (moving target indicator) radar systems, and seismology systems and the like.
In the foregoing system it may be desired to detect more than a single sequence of time spaced pulses having a given PRI. Following the techniques of the prior art delay line correlators, it would be necessary to provide a separate delay line and coincidence device for each PRI it is desired to detect which can lead to a complex and cumbersome detection system.